A portable tissue equivalent calorimeter has been designed, constructed and applied to the absolute measurement of dose in cyclotron-produced fast neutron fields at the centers carrying out neutron radiotherapy in the U.S. We will soon undertake additional measurements at the MRC cyclotron at Hammersmith Hospital in London and at the Antoni Van Leeuwenhoek Hospital in Amsterdam. It is our intention to carry out measurements of dose at the centers participating in the U.S.--Japan Cooperative Cancer Research Program, and at the two remaining U.S. institutions; NASA, Cleveland and FMI, Chicago. This effort would extend our measurements to centers which have already been visited by the radiobiology and ionization chamber intercomparison groups. The investigations will serve to improve dosimetric accuracy and will help to establish the proper dosimetric parameters to be employed in research ionization chamber measurements for radiobiology and radiotherapy.